Automatic vehicle guidance protection system

ABSTRACT

An automated vehicle protection system is provided comprising a guideway ( 20 ), a vehicle ( 10 ), a guideway loop antenna ( 21 ), and transponders ( 41   a   , 41   b ), mounted on the vehicle ( 10 ). Means ( 24, 25 ) are provided, couple to the guideway loop antenna ( 21 ), for receiving a signal from the vehicle ( 10 ) and generating an inhibit signal in order to inhibit vehicle movement in a section of the guideway ( 20 ). The inhibit signal may be passed to a circuit associated with another guideway loop antenna ( 22, 23 ) to control transmission of a signal from this other guideway loop antenna ( 22, 23 ).

CROSS-REFERENCE TO RELATED APPLICATION

This application is a U.S. national phase of International applicationPCT/GB2007/002580 filed Jul. 10, 2007, which is hereby incorporated byreference in its entirety.

A need has been identified to provide effective and sustainabletransport that is both environmentally friendly, quiet and efficient.Currently this need has been addressed by increasing use of publictransport networks such as rail and bus which offer improvements interms of pollution and efficiency over individual means of transportsuch as cars. These public transport networks have a major drawback inthat they often require a large investment in infrastructure, run to astrict time-table and times of operation are governed by working hoursof staff. In order to further improve the efficiency of these networksresearch has been conducted into automated transport networks that areable to operate 24 hours a day, are available for use by passengers atvery short notice and, most crucially, do not require a driver.

Automated vehicle guidance can be used in a passenger transport systemto provide passengers with direct point-to-point transportation. Anautomated guided vehicle is a vehicle that replaces a driver with someform of electronic intelligence allowing the vehicle to be operated bycomputer logic. Presently there are many forms of automated vehicletransport systems in operation across the world and although different,all work on a similar principle. The desired route is defined andsensors are put in place that allow the automated vehicle to follow thisroute. The defined route is delineated in any of a number of ways thatinclude following rails or magnetic loops placed in the ground,following white lines painted on a surface, sonar location, or comparingGPS and real time position data to name but a few. The path of the routecan also take a number of forms being either a linear path upon which avehicle travels back and forth or a loop of varying dimensions aroundwhich the vehicle can travel. Often multiple loops may beinter-connected in order to form a network allowing passage and travelaround one loop from another.

The vehicles themselves may use many different methods to providetraction along the guiding medium depending on the nature of theguidance medium itself; steel wheels in the case of rail guidance forexample, rubber wheels perhaps if the guiding means is placed below aroad which the vehicle is tracking along, or even an electromagneticcushion in the case of some Maglev trains.

The necessary combination of guidance means, method for providingtraction and means for sensing and responding to the guidance can takemany forms and are governed by factors of economy, technology andgeography.

As is known in the art, an important feature of an autonomous guidedvehicle is its absolute safety requirement; for example, vehicles mustbe prevented from colliding with other vehicles on the route whether thevehicles are sharing the whole of the route or just a portion common toboth in the case of networks involving many interlocking routes. In eachcase, to avoid collision between vehicles it is necessary to know theirlocation either relative to each other or to some other known referencepoint on the route and if, depending on suitably processed positiondata, a collision appears imminent then to apply some action to thevehicles to avoid the collision.

EP-A2-0330639 describes an automated guided vehicle (AGV) system inwhich a passive closed antenna loop is provided adjacent to the vehiclepath, along a length of the path and in which a transmitter on thevehicle induces an electromagnetic signal in the antenna loop. A signalinduced in the antenna loop by a first vehicle is picked up by areceiver of a second vehicle when the second vehicle is in proximity tothe antenna loop. Receipt of the signal at the second vehicle causes itto be slowed or stopped. The signal transmitted has a carrier frequencyof 73.5-76.5 kHz modulated at one of several key frequencies (1690 Hz,1090 Hz, 725 Hz, or 485 Hz). If a vehicle detects any of these keyfrequencies other than its own key frequency, this is interpreted asmeaning that there is another vehicle in the vicinity and the receivingvehicle must stop. No account is taken of and no provision made forwhether the other vehicle is upstream (i.e. following) or downstream(i.e. ahead of) the present vehicle. Presumably two such vehicles in thesame vicinity will thus cause mutual stopping, and an operator isrequired to remove the impasse.

There is a need for an improved automated guided vehicle control system,preferably having minimal trackside electronics.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention, an automated vehicleprotection system is provided comprising: a guideway for guiding avehicle along a path; a vehicle to be guided along the path; a firstguideway loop antenna for transmitting and receiving signals to and fromthe vehicle; and a transponder mounted on the vehicle for receiving asignal from the guideway loop antenna and transmitting a response to theguideway loop antenna.

Means are preferably provided, coupled to the first guideway loopantenna, for causing the antenna to transmit a sinusoidal radiofrequency signal.

Means are preferably provided in the vehicle for receiving a sinusoidalradiofrequency signal from the first guideway loop antenna andautomatically transmitting a response thereto.

Means are preferably provided coupled to the first guideway loop antennafor receiving a signal from the vehicle and selectively generating aninhibit signal in response thereto, to inhibit vehicle movement in asection of the guideway. The inhibit signal may be passed to a circuitassociated with a second guideway loop antenna to control transmissionof a signal from the second guideway loop antenna.

The first and second guideway loop antennae are preferably elongate andextend along first and second adjacent sections of the guideway.

In accordance with a second aspect of the invention, a vehicle isprovided comprising a transponder for receiving a signal from a guidewayloop antenna and responding thereto.

Code transmit means may be provided, associated with the guideway loopantenna, for selectively transmitting a code to the vehicle depending onthe presence or absence of an inhibit signal from an adjacent guidewaysection. The vehicle may have code receiving means for receiving a codefrom a guideway loop antenna and control means to cause the vehicle tomove along its guideway dependent on a code received.

In accordance with a third aspect of the invention, an automated vehicleprotection system is provided comprising: a guideway for guiding avehicle along a path; a first guideway loop antenna for transmitting andreceiving signals to and from the vehicle; and means coupled to thefirst guideway loop antenna for receiving a signal from the vehiclegenerated by the vehicle in response to a signal transmitted by thefirst guideway loop antenna and generating an inhibit signal in responsethereto, to inhibit vehicle movement in a section of the guideway.

The inhibit signal may be passed to a circuit associated with a secondguideway loop antenna to control transmission of a signal from thesecond guideway loop antenna.

The first and second guideway loop antennae are preferably elongate andextend along first and second adjacent sections of the guideway.

Code transmit means may be provided, associated with the guideway loopantenna, for selectively transmitting a code to the vehicle depending onthe presence or absence of an inhibit signal from an adjacent guidewaysection.

A preferred embodiment of the invention will now be described, by way ofexample only, with reference to the following drawings

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sporadic illustration of an AGV system in accordance with anembodiment of the invention.

FIG. 2 is a timing diagram illustrating in greater detail the timing ofthe transmission of signals in the system of FIG. 1;

FIG. 3 shows a number of intersecting AGV tracks or guideways on whichthe arrangement of FIG. 1 can be used.

FIGS. 4 and 5 illustrate normal operation with no vehicle present andwith a vehicle present, respectively.

FIG. 6 schematically illustrates an embodiment having a firstarrangement of coils and a second arrangement of coils.

DETAILED DESCRIPTION

FIG. 1 illustrates a vehicle 10 being guided along a guideway 20, whichis preferably a concrete guideway with a U-shaped cross section. Theguideway is divided into blocks of about 12.5 meters in length. Theblocks need not be of the same length. Each of the loops 20 a, 20 b and20 c has a minimum length of about 2.5 meters and a maximum length ofabout 16 meters. The width of a guideway loop is about 0.3 meters. Thereare end-to-end gaps 29 of about 0.2 meters between adjacent loops.

FIG. 1 illustrates three such blocks 20 a, 20 b and 20 c. Each block hasa single loop coil embedded in the concrete below or adjacent to theguideway. (A single loop coil is selected for ease of manufacture. Amulti-turn coil could be used.) Three such coils 21,22 and 23 areillustrated. Each coil has a respective transmitter and receiver withassociated processing electronic circuitry. Three such transceivers 24,25 and 26 are illustrated, connected to coils 21, 22 and 23respectively. As illustrated, block 20 is downstream of the movingvehicle 10 and block 20 a is upstream, with block 20 b being the currentblock in which the vehicle is passing. The respective transceivers havesignal lines passing therebetween. In particular, each upstream receiverhas a signal line for passing a “loop empty” signal to a downstreamtransceiver. Thus transceiver 26 has a signal line 30 passing totransceiver 25, and transceiver 25 has a signal line 31 passing totransceiver 24. These lines may be capable of two-way communication fortwo-way vehicle movements.

The vehicle 10 has an engine and associated control circuitry 40. Italso has: a pair of resonant (inductive/capacitive) LC circuits or“transponders” 41 a and 41 b, an FSK receiver 42, a code memory 43, anda comparator 44. The comparator 44 is coupled to the engine and itscontrol circuitry 40.

Each guideway transceiver has a programmable integrated circuit (PIC)microcontroller signal generator and detector. Each is capable ofgenerating a low frequency electromagnetic burst of simple 45 kHzsinusoidal signal. This is amplified using an RF power amplifier to asignal of about 0.1 amp to about 1 amp (preferably at the upper end ofthis range) and is transmitted into the loop (e.g. from transmitter 25to loop 22). Two vehicle-mounted LC resonant transponders 41 a and 41 b(available from Redcliffe Ltd. of 16-20 Clothier Road, Brislington,Bristol, UK) are provided, each comprising a ferrite core with a numberof turns of wire in parallel with a capacitor. They reflect signals fromthe loop 22. The provision of two such vehicle-based transpondersprovides redundancy and also serves to span the gaps 29 between adjacentloops.

Referring to FIG. 2, a burst of 45 kHz sinusoidal signal begins at timet1 and continues to time t2 (about 1.5 ms). There is then a 3 ms waitperiod during which transceiver 25 is in receive mode for receiving areflected signal 102 from a transformer 41 a or 41 b on the vehicle.Whether or not such a reflected signal is received, the process isrepeated with a second burst 103 at time t3 and the transceiver 25 waitsfor a second response 104 from the vehicle. If both return bursts 102and 104 are received by the transceiver 25, it raises its vehiclepresent signal 31 from low to high (shown at time t4). This indicates tothe upstream loop 20 a that there is a vehicle present in loop 20 b.

Continuing with loop 22, if there is no loop present signal received online 30 from downstream transceiver 26, transceiver 25 generates afrequency shift key (FSK) code signal 110 of about 8 bits, and this istransmitted through loop 22. If line 31 is high, this indicates thepresence of a vehicle in the downstream block, and no such FSK signal istransmitted.

The FSK signal transmitted is common to all vehicles and all loops (butis unique to the system). It serves to provide a signal that is clearlydistinguished from background noise.

The transmission-free period between bursts 101 and 103 is used toensure that no signal is present, thus distinguishing between noise anda genuine vehicle signal (i.e. no signal between bursts). If, therefore,burst 102 received at transceiver 25 does not end before time t3, anerror signal is generated and the process begins again at time t1.

The transponders 41 a and 41 b on the vehicle are tuned resonantinductive and capacitive parallel circuits. The provision of two suchcircuits has the benefit of reducing the risk of circuit failure, aseach transponder is completely passive. The receiver 42 on the vehiclehas separate tuned antennae (not shown), tuned to 65 kHz and 85 kHz,representing a logic 0 and logic 1 respectively. These signals aredemodulated, amplified and filtered at the receiver 42 and are thencompared to a reference code stored in a PIC based micro-controller onthe vehicle. If the code matches, the vehicle is allowed to proceed. Ifthe code fails to match or is not received at all, then a signal isapplied to the motor controller to stop the vehicle.

Referring to FIG. 3, three track loops are shown 200, 201 and 202. Thereare points are which the tracks converge and separate. The sections ofguideway 20 a, 20 b and 20 c are illustrated in this example as beingsections of guideways that are common to two tracks (track A and trackB). Equally, the arrangement can be applied where adjacent sections ofguideway served by adjacent loops span a junction. For example, blocks20 c, 20 d and 30 e span a junction. In this situation, each of blocks20 d and 20 e may provide a vehicle present signal to block 20 c.

Alternatively, a loop may entirely surround a junction, as shown byblock 20 g. In this case, block 20 g will provide a “loop empty” signalto block 20 f and to block 20 h, while block 20 g will receive a “loopempty” signal from block 20 i.

Referring to FIGS. 4 and 5, each block is capable of detecting thepresence of a vehicle within that block and transmitting its presence toa small number of following blocks (not limited to just the nextupstream block, but possibly also to one or more blocks beyond that).Each block is also capable of receiving vehicle presence signals fromthose neighbouring blocks in front, whose occupancy determines if acollision is possible if the vehicle proceeds through that block.Guideway loops are present when junctions join the main guideway, thusinhabiting vehicles attempting to join unoccupied intersection.

If one of the dual redundant transponders stops working and the vehiclestops with the remaining working unit positioned in the gap between theloop ends, there is a risk the system may not detect the vehiclepresence. A solution to this problem is to slightly overlap the ends ofthe coils 21 and 22 (and 22 and 23).

There is preferably synchronous clocking between the respectivetransceivers 24, 25, 26 etc. I.e. all t1 for one transceiver issynchronized with t1 for all other transceivers using a master clock.All transceivers send their initial bursts of a cycle at the same time.

If the vehicle were to drift, after losing control or in a wider cornersection, to one side of the track and the center mounted transpondersmoved outside the coil 15 width there is a risk the vehicle could againbe undetected. A way of solving this is to increase the number oftransponders. E.g. two transponders may be mounted at the front of thevehicle and two at the rear. Instead of pointing downwards, eachtransponder can elevated by 30°. Tests show that with two transpondersmounted at the loop width (30 cm), and sloping outwards from the topdown, the detection width is increased from 30 cm to 45 cm.

Various alternatives to the above described embodiment may be envisaged.

In one embodiment, the lengths of the loops vary along the guideway 20,each length being approximately proportional to the expected operatingspeed of the vehicle at the part of the guideway where the loop islocated. Thus at regions of the guideway 20 where the vehicle isexpected to be travelling relatively quickly, for example at straightregions, the loop lengths are longer than they are at regions of theguideway 20 where the vehicle is expected to be travelling more slowly,for example at bends. As an example, at a maximum speed on the straight,the loops are 22 m in length and at the slowest point 1 m, with varyinglengths in between.

As an alternative to the passive transponders 41 a and 41 b, activetransponders may instead be used, each comprising a simple activetransmitter and receiver arrangement.

Each guideway transceiver may be provided with an analogue digitalcontroller rather than a (PIC) microcontroller thereby removing the needfor software. It is envisaged that this may help meet the safetyintegrity standards required of automated vehicle guidance systems.

In the embodiment described with respect to FIG. 1, the guideway 20comprises a single arrangement of coils 21, 22 etc. In the alternativeembodiment illustrated in FIG. 6, the guideway 20 comprises a firstarrangement of coils (of which coils 21 and 22 are illustrated) and aseparate second arrangement of coils (of which coils 21′ and 22′) areillustrated. The first arrangement of coils and the second arrangementof coils are staggered with respect to each other such that the opposingends of adjacent coils in one of the arrangements (for example coils 21and 22 in the first arrangement) are overlapped by a respective coil inthe other of the arrangements (continuing the example, coil 21′ in thesecond arrangement). Both the first arrangement of coils and the secondarrangement of coils operate identically to the coil arrangementdescribed with respect to FIG. 1. In operation, one of the first andsecond arrangements of coils is an active arrangement whilst the otherarrangement is deactive (or redundant) and serves as a back up to theactive arrangement. If a failure is detected (or suspected in the activearrangement) the active arrangement can be closed down and the backupcoil arrangement activated. In this way the system can continue tooperate safely.

Alternatively, the first and second arrangement of coils may both beactive simultaneously so that each coil in each arrangement is capableof detecting the presence of a vehicle and transmitting this presence toupstream coils in its respective coil arrangement. Again, if one of thefirst and second coil arrangements should fail the continued operatingof the other coil arrangement means that the system can continue tooperate safely. This arrangement also mitigates the problem discussedabove with respect to FIG. 1 of the risk of non-vehicle detection shouldone of the dual redundant transponders be not working when the vehiclehas stopped with the remaining working unit positioned in the gapbetween loop ends. If, for example, a vehicle stops having a remainingworking unit positioned above the gap between coils 21 and 22 in thefirst coil arrangement, vehicle presence will still be detected by coil21′ in the second coil arrangement. Coil 21′ will then transmit avehicle present signal to at least the next upstream coil in the secondcoil arrangement to halt any following vehicle passing into the nextupstream coil prior to a collision. The signals transmitted by the firstand second coil arrangements may be at different frequencies so thatvehicles can distinguish between them.

Modifications of the invention can be made by one skilled in the artwithout departing from the scope of the invention.

1. An automated vehicle protection system comprising: a guideway forguiding a vehicle along a path, the guideway comprising a first sectionand a second section; a vehicle to be guided along the path; a firstguideway loop antenna associated with the first section of the guidewayfor transmitting and receiving signals to and from the vehicle; a secondguideway loop antenna associated with the second section of the guidewayfor transmitting and receiving signals to and from the vehicle, whereinthe first and second guideway loop antennae are configured in a seriesarrangement; a transceiver coupled to the first guideway loop antennafor receiving a signal from the vehicle and selectively generating aninhibit signal in response thereto, to inhibit vehicle movement in thesecond section of the guideway; and a transponder mounted on the vehiclefor receiving a signal from the guideway loop antenna and transmitting aresponse to the guideway loop antenna.
 2. A system according to claim 1,wherein a sinusoidal signal generator is provided, coupled to the firstguideway loop antenna, for causing the antenna to transmit a sinusoidalradio signal.
 3. A system according to claim 1, wherein a sinusoidalsignal receiver is provided in the vehicle for receiving a sinusoidalradio frequency signal from the first guideway loop antenna andautomatically transmitting a response thereto.
 4. A system according toclaim 1, wherein the inhibit signal is passed to a circuit associatedwith a second guideway loop antenna to control transmission of a signalfrom the second guideway loop antenna.
 5. A system according to claim 4,wherein the first and second guideway loop antennae are elongate andextend along first and second adjacent sections of the guideway.
 6. Asystem according to claim 1, further comprising a code transmitterassociated with the guideway loop antenna for selectively transmitting acode to the vehicle depending on the presence or absence of an inhibitsignal from an adjacent guideway section.
 7. A system according to claim1, further comprising a code receiver for receiving a code from one ofthe guideway loop antennas and a controller to cause the vehicle to movealong its guideway dependent on a code received.
 8. A system accordingto claim 1, wherein the first and second guideway loop antennae are partof a first antennae series arrangement, the system further comprising asecond antennae series arrangement distinct from the first antennaeseries arrangement, the second antennae series arrangement comprising athird guideway loop antenna and a fourth guideway loop antenna, whereinthe third guideway loop antenna is for transmitting and receivingsignals to and from the vehicle, and the system further comprising: atransceiver coupled to the third guideway loop antenna for receiving asignal from the vehicle generated by the vehicle in response to a signaltransmitted by the third guideway loop antenna and generating a secondsignal in response thereto, to inhibit vehicle movement in a section ofthe guideway, and wherein the second inhibit signal is passed to asecond circuit associated with the fourth guideway loop antenna tocontrol transmission of a signal from the fourth guideway loop antenna.9. A system according to claim 8 wherein in use the first antennaeseries arrangement is an active arrangement and the second antennaeseries arrangement is a standby arrangement that can be activated if afailure of the second antennae arrangement is detected.
 10. A systemaccording to claim 8 wherein the first and second antennae seriesarrangement are operational at the same time.
 11. A system according toclaim 8 wherein the third guideway loop antenna overlaps the first andsecond guideway loop antennae.